Gravity concentration - Different technologies

Gravimetric concentration is an important mineralurgical process. The tonnages processed in the United States by gravimetry are of the same order of magnitude as those fed by flotation. In fact, some ponderous ores (coal in its entirety and, to a lesser extent, iron) can be concentrated using gravimetric techniques. Successive concentration stages following each particle size reduction stage make it possible to take advantage of the gradual release of valuable mineral species, thus avoiding the immediate need for extensive grinding at the release mesh, which reduces energy consumption and processing costs.

These processes are ideally suited to small-scale installations, but can also handle large tonnages. What's more, they lend themselves particularly well to the installation of mobile units (on dredgers or in isolated locations).

The objectives of gravimetric concentration are :

• on the one hand, to obtain final concentrates for the extraction of coal, iron and heavy minerals such as wolframite and cassiterite;

• secondly, the production of pre-concentrates in a large number of cases (fluorite, barite, metal ores, waste treatment, etc.).This method is less affected by variations in mineralogical-chemical composition than flotation, where soluble salts, changes in mineral stoichiometry, water quality and the nature of impurities are disruptive factors.

The success of gravimetric separation depends on in-depth knowledge of the mineralogical parameters of the ore to be processed (liberation mesh size, density of the various constituents, presence of mineralogical mixtures, particle size distribution of mineral species, etc.).